JP2884054B2 - Fine processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently performing fine processing at a level of 10 nm on a substrate by dry etching using a novel means.

[0002]

2. Description of the Related Art Conventionally, electron beam lithography has been mainly used for fine processing on the nanometer scale in the manufacturing process of semiconductor devices such as ICs and LSIs. However, since this electron beam lithography method is a sequential process in which drawing is performed by scanning a focused electron beam, it takes a considerable amount of time to draw a large number of nanometer-scale dots and the like. And the throughput is low. Although fine processing by optical lithography or X-ray lithography is also known, optical lithography does not have a drawback relating to throughput, but in principle, it is difficult to form a pattern shorter than half the wavelength of light. Therefore, it cannot be used for processing at the 100 nm level. On the other hand, in the X-ray lithography method,
The resolution of the 10 nm level has not yet been achieved due to insufficient mask miniaturization.

[0003]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional lithography technique, and
An object of the present invention is to provide a method for efficiently performing m-level fine processing.

[0004]

Means for Solving the Problems The inventors of the present invention used 10n by using a method completely different from the conventional lithography technique.
As a result of intensive research to develop a method for performing micro-processing at the m level, in dry etching of a substrate, the substrate temperature is set to a temperature at which the etching gas or a reaction product of the etching gas and the substrate material starts to condense. When the substrate is set and dry-etched, the etching gas or the reaction product is partially condensed, and this serves as a nanometer-scale fine mask for etching, enabling nanometer-scale fine processing. If condensed nuclei are formed beforehand, the condensation occurs around the condensed nuclei, and it has been found that fine processing can be performed very advantageously, and the present invention has been completed based on this finding.

That is, according to the present invention, when microfabrication is performed on a substrate by dry etching, a condensation nucleus is previously formed on the substrate, and then the substrate temperature is adjusted to an etching gas or a reaction product of the etching gas and the substrate material. A microprocessing method comprising: setting a temperature at which an object starts to condense; providing a mask with a condensate formed in a desired shape by controlling the condensation conditions on the substrate; and simultaneously performing a dry etching process on the substrate. Is provided.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The substrate material used in the present invention may be selected from metals, alloys, ceramics and the like which have been generally used as substrates in the fields of the electronics industry, the printing plate manufacturing field and the mechanical fine processing field. It can be arbitrarily selected and there is no particular limitation. Such materials include, for example, aluminum, tungsten, titanium, cobalt, iron, silicon and alloys thereof, silicon nitride, gallium-arsenic, titanium oxide, silicon oxide, glass and the like. Is preferably used.

In the present invention, when these substrates are subjected to fine processing by dry etching, the substrate temperature is set to a temperature at which an etching gas or a reaction product of the etching gas and the substrate material starts to condense (hereinafter, referred to as a temperature). (Referred to as condensation start temperature). If dry etching is performed at this condensation start temperature, the etching gas or the reaction product of the etching gas and the substrate material will be partially condensed, and this will serve as a nanometer-scale fine mask for etching, enabling desired fine processing. Becomes At this time, if a condensed nucleus having a desired pattern is formed on the substrate in advance and then dry etching is performed, the condensed nucleus is centered on the condensed nucleus. Is etched and finely processed into a desired pattern.

FIG. 1 is a process explanatory view of an example of a method for performing fine processing on a substrate according to the present invention. First, a condensation nucleus 2 having a desired pattern is formed on a substrate 1 (A), and then condensation starts. By performing a dry etching process at a temperature, portions where no condensation nuclei are provided are selectively etched,
A pattern 3 is formed (b).

Here, the dry etching process is to etch a substrate by forming a reaction product having a high vapor pressure by a reaction between an etching gas and the substrate. This dry etching process is generally performed under a reduced pressure gas phase, and plasma is often used to generate reactive species.

FIG. 2 is a diagram showing the principle of the method of the present invention. As shown in this figure, the reactive species (B) hit the substrate (A) and the reaction product (C) is desorbed, whereby the etching proceeds. When the substrate is cooled to the condensation start temperature during the etching process, the reaction product or the etching gas (D) condenses on the substrate surface. However, this condensation does not occur uniformly over the entire surface of the substrate, but starts at a nucleus at a singular point such as micro unevenness or an attached matter on the substrate. This singularity may exist naturally, but if a condensation nucleus is artificially provided on the substrate, the etching gas (D) or the reaction product (C) can be selectively condensed. The condensation start temperature depends on the type and pressure of gas, the type of substrate, the density of plasma and its temperature, and the state of the substrate. If the substrate temperature is too low, condensation will occur over the entire surface and etching will not proceed at all. On the other hand, if the substrate temperature is too high, no condensation occurs, and the entire surface of the substrate is uniformly etched. Therefore, it is important that the substrate temperature is set to a temperature at which condensation occurs only in a place where the intermediate condensation nucleus exists. The size of the condensate condensed in the condensed nuclei depends on the substrate temperature and the affinity between the substrate and the condensate, but if the conditions are controlled, a relatively uniform product can be obtained. Can be Since this condensate acts as a mask for etching, fine processing on a 10 nm scale can be performed.

As described above, even if no condensation nuclei are formed artificially, the substrate can be subjected to fine processing on a 10 nm scale by performing dry etching while maintaining the substrate temperature at the condensation start temperature. However, when no condensation nuclei are formed, the setting of the condensation start temperature is extremely sensitive to the etching conditions, the reproducibility is poor, and it is difficult to control the density of the formed condensate. Therefore, in the present invention, it is necessary to artificially form condensation nuclei on the substrate in advance.

As described above, the method of forming the condensation nuclei may be such that microscopic irregularities or deposits are distributed on the substrate, and there is no particular limitation. A thin film of a soluble organic polymer substance is provided, and a pressure is applied to a part of the thin film to make it insoluble, and then a portion to which no pressure is applied is selectively dissolved and removed with an organic solvent to form a fine pattern condensation nucleus. (2) A method of forming fine condensed nuclei by applying fine mechanical damage to a substrate, (3)
A method of depositing metal on a substrate and forming condensation nuclei,
(4) A method of irradiating the substrate with an ion beam or an electron beam to form condensation nuclei.

Next, first, in the method of forming condensation nuclei of the above (1), the organic polymer substance used for forming a thin film on the substrate is soluble in a certain organic solvent, Can be arbitrarily selected from those having a certain degree of adhesiveness between them, and especially those whose molecular weight is increased by pressurization, those which become insoluble or hardly soluble in organic solvents due to densification, or those with substrates. It is preferable that the organic solvent be firmly adhered to and hardly soluble in an organic solvent.

Examples of such an organic polymer substance include:
Olefins such as ethylene, propylene, butylene, styrene, aromatic vinyl compounds such as α-methylstyrene, acrylic acid, methacrylic acid, 2-phenylacrylic acid, 2-acetylacrylic acid, maleic acid, fumaric acid Unsaturated carboxylic acid, unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, acrylamide, methacrylamide, 2- Functional derivatives of unsaturated carboxylic acids such as phenylacrylamide, unsaturated carboxylic acid amides such as 2-acetylacrylamide, unsaturated carboxylic anhydrides such as maleic anhydride, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile , Methacrylonitrile Which unsaturated consisting of at least one monomer selected from compounds may be mentioned polymers or copolymers.

Among them, (meth) acrylate polymers such as polyethyl acrylate and polymethyl methacrylate, and styrene resins such as polystyrene are particularly preferred. The molecular weight of the polymer or copolymer is preferably in the range of 1,000 to 2,000,000.

In order to form a thin film of an organic polymer substance on a substrate, for example, the above-mentioned polymer or copolymer is dissolved in an appropriate solvent to prepare a coating solution, which is coated on the substrate by a spinner or the like. ,dry. The thickness of the organic polymer compound thin film is usually selected in the range of 10 to 100 nm.

Next, when a pressure is applied to the organic polymer substance thin film provided on the substrate in a desired pattern according to a desired pattern, the portion is firmly bonded to the substrate and becomes insoluble or hardly soluble. Even if the polymer material in the portion to which no pressure is applied is dissolved and removed by the solvent treatment, the polymer material in the fixed portion is not dissolved and remains on the substrate. The fixing density of the polymer is higher as the applied pressure is higher, and when the pressure is not too high, a fine pattern of about the size of the molecule is formed because each of the polymers is individually fixed. Is done. That is, even if pressure is applied to the entire surface of the substrate using hydrostatic pressure or the like, a fine pattern in which fine dots of a size similar to that of a polymer are distributed over the entire surface can be created. Also, if pressure is applied according to a predetermined pattern, the polymer substance fixed at a density corresponding to the applied pressure is distributed in the area where the pressure is applied, so that a fine pattern in which a large number of fine dots are distributed in the predetermined area. It is formed. Here, if the size of the polymer substance is controlled, the size of the dot can also be controlled. In addition, if the pressure is sufficiently high, the polymer substance adheres to the entire area where the pressure is applied, so that a pattern according to the pattern of the applied pressure can be formed. Furthermore, by devising a means for applying pressure, a plurality of patterns can be drawn in parallel, so that the throughput can be increased.

The organic solvent for dissolving and removing the thin film of the organic polymer material in the portion where no pressure is applied is not particularly limited as long as it can dissolve the polymer material.
For example, when the polymer substance is made of polymethyl methacrylate, acetone, methyl ethyl ketone, diethyl ketone and a mixture thereof are used, and when the polymer substance is made of polystyrene, an aromatic solvent such as toluene is used. . As a method for dissolving and removing the thin film of the organic polymer substance in a portion where no pressure is applied using the organic solvent, a dipping method is usually used.

In the present invention, as a method for applying pressure on the thin film of the polymer substance, a method of simply pressing the polymer film from above with a needle or the like or a method of scratching the polymer film with a needle can be used. In this case, the density of the polymer substance to be fixed depends on the pressure at the time of scratching, and as the pressure is increased, the density increases, but if the pressure is too large, the substrate itself is damaged or the polymer substance is pressed. In some cases, the action of peeling off is also stronger, and the fixing density may be lower. The applied pressure cannot be determined unequivocally because it depends sensitively on the type of thin film of the organic polymer substance, the material of the substrate, and the micro shape of the needle tip, but, for example, it is provided on a silicon substrate. 12μ polymethyl methacrylate film
When scratching with a m diameter diamond needle, 1-100g
Needle pressure, preferably in the range of 5 to 30 g.

In such a method of scratching with a needle,
The microscopic position of the dot by the fixed polymer is not controlled, but the macroscopic position can be controlled, and the fixing density can also be controlled by the pressure. Therefore,
This method does not matter which microscopic position is within a predetermined range, but is extremely advantageous when it is necessary to form an extremely large number of dot patterns.

When it is necessary to control the microscopic position, a pressure is applied to a predetermined position using a needle whose tip is finely processed to form a fine pattern having a controlled microscopic position. can do. For example, if the tip of the needle is finely processed and pressed against the organic polymer film using this, the pattern processed at the tip of the needle is transferred onto the organic polymer film.
In addition, scratching the polymer film with this needle is equivalent to scratching with the number of fine needles corresponding to the number of irregularities on the needle tip. A row of appropriate dots is formed. Further, by increasing the pressure at the time of the scratching so that the fixation density increases as the dots are connected, a fine line can be drawn.

Further, using an atomic force microscope (AFM),
The tips of the needles of the probe may be sequentially pressed so as to form rows of dots on the organic polymer film, and the polymer film may be fixed to the substrate to form a fine pattern. The fine pattern formed of a thin film of a polymer substance formed in this way effectively acts as a condensation nucleus.

On the other hand, in the method (2) for forming condensation nuclei, fine mechanical damage is applied to the substrate,
Form condensation nuclei. As a method of performing the mechanical damage, for example, a method of scratching the substrate with a needle as in the case of the above (1) can be used. In such a method of scratching with a needle, it is difficult to control the microscopic position of the formed damage, but it is possible to control the macroscopic position and also to control the density. Therefore, this method is not limited to a microscopic position in a predetermined range, but is advantageous when it is necessary to form an extremely large number of dot patterns.

If it is necessary to control the microscopic position, the substrate may be scratched using a needle whose tip is finely processed, as in the case of (1). Alternatively, the substrate may be scratched with the probe needle using an atomic force microscope (AFM). The damage on the substrate thus formed effectively acts as condensation nuclei.

Next, in the method (3) for forming condensation nuclei, a metal is deposited on a substrate,
Form condensation nuclei. When a metal such as gold or a gold-palladium alloy is deposited by a sputtering method or a vacuum evaporation method, and a thin film having a thickness of about several nm in average film thickness is provided,
These metals form nanometer-scale island-like structures on the substrate and act as condensation nuclei. In this case, the microscopic position of the formed condensation nucleus is not controlled, but the macroscopic position can be controlled.

When it is necessary to control the microscopic position, for example, a scanning tunneling microscope is used, a voltage is applied between the probe and the substrate, and the metal atoms of the probe are evaporated by electric field. Advantageously, a method of depositing a metal on a substrate is used. The metal deposited on the substrate in this way effectively acts as condensation nuclei.

Further, in the method (4) for forming condensation nuclei, the substrate is irradiated with an ion beam or an electron beam to form condensation nuclei. When the substrate is irradiated with an ion beam or an electron beam, the irradiated portion is damaged, or a gas remaining in a chamber of the irradiation apparatus is decomposed by the ion beam or the electron beam and deposited. Therefore, the surface state of the substrate differs between the irradiated part and the non-irradiated part, and the irradiated part effectively acts as a condensation nucleus. Such a method of irradiating an ion beam or an electron beam can control a microscopic position of a condensation nucleus.

In the fine processing method of the present invention, a substrate,
In particular, the substrate provided with the condensation nuclei on the surface as described above is subjected to a dry etching treatment at a condensation start temperature. As the dry etching treatment method, an electron cyclotron resonance (ECR) etching apparatus is particularly used. Is advantageous. According to this method, since it is possible to perform etching without increasing the energy of ions too much, the etching gas or reaction product condensate attached to the condensation nucleus is not destroyed by ion bombardment, and is used as a mask. Can work. When a silicon substrate is used as the etching gas, sulfur hexafluoride is particularly preferable.

[0029]

According to the present invention, 10n is achieved without using a lithography technique conventionally used in microfabrication.
m-level fine processing can be performed efficiently.

[0030]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1 A silicon substrate had a weight average molecular weight of about 600,000 and a dispersity of 3
The following polymethyl methacrylate (PMMA) thin film was formed with a thickness of 75 nm by spin coating. Then
50 g of this thin film with a tungsten needle having a tip diameter of 50 μm
And then immersed in acetone for 2 minutes.

Next, the sample was placed in an electron cyclotron resonance (ECR) etching apparatus, and was subjected to a dry etching treatment (etching gas: SF ₆ 1 × 10 ⁻⁴ torr,
Microwave: 2.45 GHz, 250 W, 13.
A high frequency of 5 MHz of 5 MHz was applied for 1 minute.

When the sample temperature was set at -140 ° C., condensation occurred on the entire surface and was not etched. When the sample temperature was set to -120 ° C, the entire surface was uniformly etched. Further, when the sample temperature was set to -130 ° C., a silicon pillar having a diameter of about 10 nm was formed at a location where the needle was scratched. Therefore, the condensation start temperature is evaluated to be -130 ° C in this case.

FIG. 3 shows the distribution of diameters of the formed silicon pillars. The diameter distribution extends from 7 to 17 nm and averages 1
1 nm, standard deviation 2.5 nm. Also, PMMA
Was carried out in the same manner as above using polystyrene having a weight average molecular weight of about 1,000,000 instead of
m, a silicon pillar having a height of about 100 nm was formed.

Example 2 Gold was deposited to a thickness of 1 nm on a silicon substrate by sputtering. This sample was placed in an ECR etching apparatus, the sample was cooled to −130 ° C., and dry etching was performed using gold particles as condensation nuclei (sample temperature: −130 ° C.).
° C, etching gas: SF ₆ 1 × 10 ^-4 torr, microwave: 2.45 GHz, 250 W, 13.56 for the sample
(A high frequency of 5 MHz was applied) for 1 minute. As a result, a silicon pillar having a diameter of about 10 nm was formed.

Example 3 A silicon substrate whose surface was cleaned with hydrogen fluoride was
The tip was scratched with a tungsten needle having a tip diameter of 50 μm at a needle pressure of 50 g. Next, when this sample was subjected to dry etching in the same manner as in Example 2, a silicon pillar having a diameter of about 10 nm was formed.

Example 4 A silicon substrate whose surface was washed with hydrogen fluoride was
Focus the beam to 30 nm with a focused ion beam device 70
Irradiation with keV gold ions was performed at 10 ¹³ / cm ² . When this sample was dry-etched in the same manner as in Example 2, the place where the ions were implanted functioned as a condensation nucleus, and a silicon pillar having a width of 30 nm was formed.

Example 5 A silicon substrate whose surface was washed with hydrogen fluoride was
20 keV electron beam is narrowed down to 10 nm, 0.01 C / c
Irradiation was performed at 2000 points with an irradiation amount of m ² . When this sample was dry-etched in the same manner as in Example 2, a silicon pillar having a width of 10 nm
00 pieces were formed.

Example 6 Gold dots were deposited on a silicon substrate whose surface was washed with hydrogen fluoride by electric field evaporation using a scanning tunneling microscope using gold as a probe. The field evaporation was performed by applying a voltage so that the sample bias was -4 V, the tunnel current was 10 nA, and the pulse width was 10 ms.
When this sample was dry-etched in the same manner as in Example 2, a silicon dot having a diameter of about 10 nm was formed at the position where gold was deposited.

Example 7 On a silicon substrate, a weight average molecular weight of about 600,000 and a dispersity of 3
The following PMMA thin films were formed with a thickness of 75 nm by spin coating. Next, the tip of a probe needle of an atomic force microscope (AFM) is pressed against the thin film, and 10 GPs are sequentially formed so that a dot line in which one point is arranged in one line is formed.
a pressure was applied. Next, the sample was immersed in acetone for 2 minutes, and then the sample was subjected to dry etching in the same manner as in Example 2. As a result, a row of silicon dots having a diameter of about 10 nm was formed at a predetermined location.

[Brief description of the drawings]

FIG. 1 is a process explanatory view of one example of a fine processing method according to the present invention.

FIG. 2 is a view showing the principle of a fine processing method according to the present invention.

FIG. 3 is a graph showing a distribution of diameters of silicon pillars formed in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Condensation nucleus 3 Fine pattern formed after dry etching

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-241126 (JP, A) JP-A-4-341555 (JP, A) JP-A-8-316917 (JP, A) Edited by Tokuyama Wei, Integrated Circuit Process Technology Series Semiconductor Dry Etching Technology, "First Edition, Sangyo Tosho Co., Ltd., October 6, 1992, p. 333 (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/3065 H01L 21/30

Claims (8)

(57) [Claims] When performing fine processing on a substrate by dry etching, after forming condensation nuclei on the substrate in advance, the substrate temperature is reduced to an etching gas or a reaction product of the etching gas and the substrate material is condensed. A fine processing method characterized by providing a mask with a condensate formed in a desired shape by setting a temperature at which to start and controlling a condensation condition on the substrate, and simultaneously performing a dry etching process on the substrate. 2. A thin film of an organic polymer substance soluble in an organic solvent is provided on a substrate, a pressure is applied to a part of the thin film to make it insoluble, and a portion to which no pressure is applied is selectively treated with an organic solvent. 2. The fine processing method according to claim 1, wherein the fine pattern is formed by dissolving and removing the nuclei. 3. The fine processing method according to claim 2, wherein the organic polymer substance soluble in the organic solvent is an acrylate polymer, a methacrylate polymer or a styrene resin. 4. The fine processing method according to claim 1, wherein minute mechanical damage is applied to the substrate to form condensation nuclei. 5. The method according to claim 1, wherein metal is deposited on the substrate to form condensation nuclei. 6. The fine processing method according to claim 1, wherein the substrate is irradiated with an ion beam or an electron beam to form condensation nuclei. 7. The fine processing method according to claim 1, wherein the dry etching process is performed using an electron cyclotron resonance (ECR) etching apparatus. 8. The fine processing method according to claim 1, wherein fine processing at a level of 10 nm is performed.